1. Field of the Invention
The present invention relates to an input device of a vehicle brake system.
2. Description of the Invention
As a brake system for a vehicle (automobile), there has been known, for example, one including a servo unit such as a vacuum booster or a hydraulic booster. In recent years, there has been known an electric booster driven by an electric motor (See, for example, Japanese Unexamined Patent Application Publication No. 2010-23594, hereinafter referred to as Publication 1).
The electric booster of the Publication 1 includes a main piston, a booster piston, and an electric motor. The main piston moves forward and rearward when a driver operates a brake pedal. The main piston is cylindrically shaped, and fitted in the booster piston to be displaced relative to the main piston. The electric motor drives the booster piston.
In this electric booster, the main piston and the booster piston serve as pistons of a master cylinder, and have respective front end portions located inside a pressure chamber of the master cylinder. The main piston is imparted a thrust by the driver's operation of the brake pedal and the booster piston is imparted a booster thrust by the electric motor to generate a brake fluid pressure in the master cylinder.
In the electric booster of the Publication 1, however, since a mechanism of imparting the brake pedal thrust and a mechanism of imparting the electric motor booster thrust are configured as an integral unit, the entire size thereof tends to be increased, which leads to a reduction in the possibility of the layout of a brake system that includes the electric booster of the Publication 1.
The present invention has been made to solve the above-mentioned problem and it is an object of the present invention to provide an input device of a vehicle brake system that can increase the possibility of the layout of the vehicle brake system.